Multiple tray drier



Dec. 5, 1967 D. R. GESKE 3,355,814

MULTIPLE TRAY DRIER Filed Feb. 15, 1966 4 Sheets-Sheet 1 3 INVENTOR.

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ATTORNEYS 4 Sheets-Shee t 4 Filed Feb. 15, 1966 m T WM %W m/ V 4 I W Y B aw United States Patent 3,355,814 MULTIPLE TRAY DRIER Darel R. Geske, Hopkins, Minn., assignor to The Mead Corporation, Dayton, Ohio, a corporation of Ohio Filed Feb. 15, 1966, Ser. No. 527,449 2 Claims. (Cl. 34-22) ABSTRACT OF THE DISCLOSURE A drying method and apparatus wherein heated fluid is caused to have a translational movement along a sinuous path within a drying chamber through which material to be dried is moved in a direction opposite to the general direction of movement of the heated fluid.

The present invention relates generally to the drying of moisture laden material or objects and, more particularly, to an improved system, method and apparatus for the removal of moisture from moisture laden material or objects.

Prior to the present invention, many methods, systems, apparatus, etc. have been employed for the removal of moisture from material or objects with varying degrees of success. In general, all such prior art methods and/or apparatus are subject to one or more disadvantages, a partial listing of which includes operable but inefiicient or time consuming, excessive plant space requirements, excessive plant investment requirements regarding expensive and/ or complicated apparatus and/or controls. Accordingly, an object of the invention is to obviate the above mentioned difficulties.

Another object is to provide an improved drying method and apparatus and having improved efiiciency of moisture removal.

Another object is to provide an improved drying method and apparatus in which only mechanically simple components are employed and in which operational costs are minimized.

A further object is in the provision of improved drying method and apparatus wherein the required number of operating personnel is minimized and wherein unskilled labor can be utilized.

An additional object is to provide an improved drying method and apparatus capable of handling, in a given amount of industrial floor space, an increased drying load or, alternatively, for handling a given drying load with a reduced floor space requirement.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a fragmentary plan sectional View of a drying system and illustrating diagrammatically directions of air flow and of mechanical movement;

FIGURE 2 is a partial longitudinal section view in the direction of the arrows 22 of FIGURE 1;

FIGURE 3 is a cross section in the direction of the arrows 3-3 of FIGURE 2;

FIGURE 4 is an elevational view, partly in section, in an apparatus embodiment of the invention;

FIGURE 5 is an enlarged schematic fragmentary plan view illustrating various mechanical movements;

FIGURE 6 is a schematic control diagram for certain turn-around and feeding portions of apparatus embodying the invention; and,

FIGURE 7 is a schematic control diagram for certain feeding portions and the level selector portion of apparatus embodying the invention.

As illustrated in the drawings, practice of the invention includes, in general, placing material or objects to be dried upon a tray 10 having a mesh or foraminous 3,355,814 Patented Dec. 5, 1967 bottom 11 to provide maximum exposed surface of said material or objects during a drying operation. When tray 10 has been loaded with such material or objects at a loading station 12, the tray is advanced to a waiting station 13 until tray 10 can be received onto a level selector 14 which either raises or lowers the loaded tray to a selectable level at which the tray is then inserted into the entrance end of a drier 15. Upon completion of the drying operation, the tray and its contents are removed from the opposite end of the drier and the: contents removed. The empty tray 10 is then returned to the entrance end of the oven by a return chute 16 and conveyors 17, 18 which turn the tray 10 at a turn station 19 to a position substantially normal to the longitudinal axis of the terminal portion of the chute. The empty tray is then pushed by a piston and cylinder unit 20 from turn station 19 to a ready station 21 where it remains until the above cycle is to be repeated, at which time the tray is moved by a conveyor 22 to the loading station 12.

Drier 15 includes bottom wall 23, side walls 24, 25, top Wall 26, and an intermediate wall 27 connected between side walls 24, 25. Wall 27 extends substantially the entire length of the drier and thus divides the interior thereof into an upper drying chamber 28 disposed above a lower heating chamber 29.

Heated air or other suitable fluent material is supplied to heating chamber 29 by an inlet duct 30. The heated air or other fluent material is conveyed from chamber 29 and supplied to and distributed in drying chamber 28 in a manner which will be described in greater detail as the description proceeds. The fluent material is removed from chamber 28 through an opening or port 31 in wall 25 and is received into a duct 32 connected to an exhaust fan 33.

As is best illustrated in FIGURES 2 and 4, a plurality of tracks or rails 34 are provided to support trays 10 and to guide their movement through the drier. Tracks or rails 34 are arranged in oppositely disposed pairs with one rail of each pair secured to side walls 24, 25. Hence, when a tray 10 is received onto a particular pair of tracks or rails 34, it is supported and guided thereby throughout its course of movement through drier 15. The several pairs of tracks or rails 34 are disposed at different levels above or below each other. While there are live different levels illustrated and described herein, it is to be understood that the number of levels may be increased or decreased as desired and that the invention is not limited to any particular number of levels.

The material or objects to be dried carried by trays 10 travel through the drier in the direction indicated by arrow 35. In accordance with the invention, drying is effected by establishing within drying chamber 28 a generally sinuous or zig-zag flow path of heated air or other heated fluent material from side-to-side between side walls 24, 25 and in a general direction opposite to the direction of travel of trays 10. Such a flow path is established by the provision of a plurality of spaced apart discharge ports and ducts 36, 37, respectively. Ports 36 are vertically disposed in side wall 24 and extend substantially from top Wall 26 to intermediate wall 27 to direct heated fluent material into chamber 28 in the direction indicated by arrows 38. The heated fluent material is drawn from heat chamber 29 through a plurality or spaced apart inlet ducts 39 by blowers 40. Similarly disposed and extending in side Wall 25 are correspondingly spaced apart discharge ports and ducts 41, 42 respectively. Ports 41 receive heated fluent material drawn from chamber 29 through ducts 43 -by blowers 44 and discharge into chamber 28 in the direction indicated by arrows 45. Flexible boundary material 46, 47 is provided at the entrance and exit openings, respectively, to provide a seal and yet allow entry and exit of trays 10.

An empty tray is placed upon a table member 48 supported at a convenient level by a support member 49. The tray remains at this loading station 12 during the period of time required to place material or objects to be driedupon the tray. When the tray has been loaded with such material or objects, it is pushed from tray loading station 12. to an adjacent waiting station 13. The now loaded tray 10 remains at waiting station 13' until it can be received by the level selector 14. When the level selector is in position to receive a loaded tray, an endless belt or chain type of feeding device 50 driven by an electric motor (not shown) is rendered operable by means of a known starting circuit to feed or push loaded tray 19 from Waiting station 13 onto level selector 14. While in FIGURE 4, feeding device 50 is illustrated at station 13, thus requiring tray 10 to be pushed manually from station 12 to station 13, if desired, the feeding device 50' can be extended to perform the pushing or feeding operation between stations 12 and 13 as well as between station 13 and level selector 14.

In accordance with the invention, means are provided for receiving a loaded tray 1t from loading station 12 and waiting station 13 and at the level thereof as established by the height of table member 48 which provides the support for both such stations, then either elevating or lowering said tray to a selectable desired level and in alignment with the level of a corresponding pair of tracks or rails 34 in drier l5, thereafter feeding said tray into the drier automatically, returning to receive a subsequent loaded tray 10 from and at the level of station 13, and thereafter automatically repeating such cycle with subsequent trays which continue to be fed into the drier at said selectable level until a new level has been selected or operation discontinued by an operator.

Such level selector and feed means include frame members 51 which provide support and lateral guidance of a vertically reciprocable table member 52 upon which are mounted a pair of tracks or rails 53 spaced apart corresponding to the spacing between the several pairs of tracks or rails 34 secured to the drier side walls 24, 25 for alignment with rails 34 when table 52 is at the proper elevation. Reciprocation of table member 52 to either elevate or lower it to a desired level is accomplished by a reciprocable piston and cylinder lift unit 54 including a motor driven hydraulic pump 55, a solenoid control 56, and a piston rod 57 connected to the piston and to the lower side of table member 52. Lift unit 54 is presently a commercially available item and, hence, will not be further described except to note that when motor driven pump 55 is operating, hydraulic fluid under pressure is supplied to the piston which causes it to move; the piston is returned to its initial position, with the pump 55 inoperative, by energizing solenoid control 56 which opens a valve to release fluid pressure applied to the piston.

An endless belt or chain type of feeding device 58 driven by an electric motor 59 is provided to urge or push a loaded tray 10 from level selector table 52 into drier 15. Feeding device 58 is connected to table 52 and thus moves with the table. Alternatively, if desired, the feeding device may comprise a plurality of devices 58 each connected to frame members 51 at a level corresponding to a level of rails 34 of drier 15.

Thus, pump 55 is operated to elevate table 52 to a desired level; solenoid control 56 is energized to lower table 52 to a desired level; and motor 59 is operated to to cause feeding device 58 to push a tray 10 into drier 15.

The invention includes the provision of means for assuring that the various steps occur in proper sequence and to mal ce the apparatus incapable of operation until prerequisite conditions are met and prior steps have been properly completed. The control diagram for level selection and feed is shown in FIGURE 7.

For example, since automatic operation is desired, it is equally desirable to prevent the commencement of a level selecting cycle until tray 10 is properly positioned on elevator table 52. Accordingly, a switch 60 having a pair of normally open contacts 60U is connected in series relation with the energizing circuit for the motor of pump 55, and having a pair of normally open contacts 60D is similarly connected with the energizing circuit for solenoid 56. Switch 60 is mounted on elevator table 52 in a location such that its normally open contacts will be closed when a tray 10 is properly positioned on the table. Hence, neither pump 55 nor solenoid 56 can be initially energized until a tray 10 is in proper position.

A switch 61 also of the type that is actuated by physical contact is also mounted on table 52 to perform the dual function of stopping the movement of table 52 at a selectable level corresponding with one of the several levels of rails 34 of drier 15 and simultaneously initiating operation of the motor 59 of feeding device 58 to push a tray 10 into the drier at the selected level. Switch 61 has two sets of normally closed contacts 61U, 61D, and a set of normally open contacts 61F. When switch 61 is actuated by physical contact, the action of all three of its sets of contacts is simultaneous, i.e., contacts 61U and 61D will open and contacts 611 will close, simultaneously.

A selector switch 62. having five selectable contacts 62(1)-6 2 (5), inclusive, corresponding to the number of different levels of rails 34 in drier 15, and a sixth contact 62(L), which is connected to a suitable source of electrical energy, is provided to select a particular level at which it is desired to insert trays 10 into drier 15. As illustrated, contacts 62(3), 62(4) and 62(5) are parallel connected to line 63 having normally open contacts 6tlU and normally closed contacts 61U series connected therewith and with the coil of a magnetic starter or relay 64. The normally open contacts 64-U of starter are series connected with lines 65 66 to energize motor-pump 55 when contacts 64U are closed. Hence, selector switch positions 3, 4 or 5 elevate table 52. Similarly, contacts 62(1) and 62(2) of selector switch 62 are parallel connected to line 67 having normally open contacts 60D and normally closed contacts 61]) series connected therewith and leading to solenoid 56. Hence, selector switch posi tions 1 and .2 lower table 52.

Once table 52 has been started in either an upward or a downward direction, it must be stopped when it reaches a level corresponding to that selected by the position of selector switch 62. This is accomplished by actuating switch 61 when table 52 is at the desired level and thus opening normally closed contacts 6'1U and 61D and thereby interrupting either line 63 or line 67, as the case may be. As noted above, the action of all sets of contacts of switch 61 is simultaneous. Hence, when contacts 61U and 61D become open, contacts 61F become closed and initiate operation of motor 59 by completing line 68 and thereby energizing the coil of a magnetic starter or relay 69, thus causing normally open contacts thereof to close and complete a power supply circuit to motor 59.

In accordance with the invention, provision is made for the physical actuation of switch 61 only when table 52 reaches the desired selectable level and without physi cal actuation thereof when the table passes non sel'ected levels that may be disposed between the level of waiting station 13 and the desired level. This is accomplished by the provision of five different level position sensing devices 70-74 inclusive, each of which is connected to a particular one of contacts 62(1)-62(5) of selector switch 62. Each of the level position sensing devices 7tl'74 inclusive comprises a reciprocable piston and pneumatic cylinder unit 700, 71c, 72c, 73c and 74a with operation of each such unit being controlled by a solenoidcontrolled valve 70s, 71s, 72s, 73s and 74s for causing the piston to move to an extended position or to a retracted position depending upon whether the solenoid is energized or not. Selective control is thus provided by connecting solenoid 70s to contacts 62(1); solenoid 71s to contacts 62(2); '72s to 62(3); 73s to 62(4), and solenoid 74s to contacts 62(5), as indicated in FIGURE 7.

Selector switch 62 is a presently available commercial item but is of special design and thus differs from conventional selector switches. For example, a selector switch having the features of switch 62 can be obtained from Micro Switch Division of Honeywell, Inc., in which five DT-2RV22A7 Micro Switches are employed. The principal diiference between selector switch 62 and an ordinary selector switch is that in switch 62 the parallel connection, shown in FIGURE 7, between contacts 62(1) and 62(2), as well as the similar connection between contacts 62(3), 62(4) and 62(5), is interrupted so that a completed circuit exists only between contact 62(L) and a single one of the several contacts 62(1)62(5). Thus, with switch 62 in the first position thereof, electrical energy is supplied from contact 62(L) to contact 62(1) but not to contact 62(2). Similarly, with switch 62 in its fourth position, electrical energy is supplied from contact 62(L) to contact 62(4) but not to contacts 62(3) nor to 62(5). Hence, at any particular setting of switch 62 only one of solenoids 70s-74s is energized.

Cylinder units 70c-74c are mounted so that in the extended position thereof, physical engagement will occur with switch 61 to actuate its contacts when table 52, upon which it is mounted, reaches a desired level. Accordingly, cylinder unit 71c is mounted so that the extended position thereof will actuate switch 61 and stop table movement when table 52 is at a position with table rails 53 in proper alignment with the lowermost rails 34 of drier 15. Units 71c-74c are each mounted for actuation, in the extended positions thereof, of switch 61 at a position corresponding with alignment with the next higher rails 34. As illustrated and described, the level of table 52, when aligned to receive a tray from waiting station 13, is at a position intermediate between the second and third levels of drier rails 34; hence, such level is between those levels established by selector switch positions 2 and 3.

After a tray 10 has been delivered and fed into drier at a selected level, table 52 must be returned to its initial position to receive a subsequent tray from waiting station 13. However, since the initial tray has been pushed from table 52 into the oven, the contacts 60U and 60D are then open. Accordingly, the piston and cylinder unit 54 cannot be rendered operable to move the table in either an up or a down direction through the now open lines 63 or 67. Additionally, it is to be noted that the return movement of table 52 must be in a direction opposite to its initial movement.

A magnetic starter 75 having two sets of normally open contacts 75(1) and 75(2) provides an additional means for supplying energy from line 65 to drive pump 55 through line 76 when contacts 75(1) are closed. The coil of starter 75 is connected to one of contacts 75(2) and is energized by line 77 connecting said one of contacts 75(2) and parallel connected switch contacts 62(1) and 62(2) and having switches 78 and 79 connected in series in line 77. Switch 78 has two sets of normally closed contacts 78(1) and 78(2). Similarly, switch 79 has two sets of contacts 79(1) and (79(2) but these are normally open contacts. Normally closed contacts 78(1) and normally open contacts 79(1) are the portions of switches 78 and 79 that are series connected in line 77.

A magnetic starter or relay 80', similar to starter 75, and having two sets of normally open contacts 80(1) and 80(2) provides an additional means for supplying energy from line 65 to energize solenoid 56 through a line 81 when contacts 80(1) are closed. The coil of starter or relay 80 is connected to one of contacts 80(2) and is energized by a line 82 connecting said one of contacts 80(2) and parallel connected to selector switch contacts 62(3), 62(4) and 62(5) and having normally closed contacts 78(2) and normally open contacts 79(2) connected in series in line 82.

Starter or relay 54 is energized to initiate an upward movement of elevator table 52 by supplying energy to the pump 55 by means of line 66. No holding circuit is provided so that initial upward movement of the elevated table 52 will continue only so long as the coil of relay 64 remains energized. Similarly, no holding circuit is provided to maintain solenoid 56 in an energized condition with respect to an initial downward movement of the elevator table so that either an initial upward movement or an initial downward movement will continue only so long as either line 63 or line 67 constitues an uninterrupted circuit through switches 60, 61. However, after an initial upward or downward movement of the elevator table to a desired selected level, once a return movement of the elevator table is initiated, the elevator table should continue to move until the table has returned to its initial level and is thus able to receive a subsequent tray 10 from and at the level of the waiting station 13. Accordingly, holding circuits are provided for maintaining the coils of starter relays 75, in an energized condition. This is accomplished by connecting the coil of relay 75 to the one of contacts 75(2) that is connected to line 77. The other one of contacts 75(2) is connected by a line 83 to line 77 at a location between the normally open contacts 79(1) and the normally closed contacts 78(1). Thus, the coil of relay 75 is initially energized by line 77 through series connected contacts 78(1) and series connected contacts 79( 1) and is maintained in an energized condition by means of line 83 and normally open contacts 75(2) which are closed once the coil is initially energized.

Similarly, the coil of starter relay 80 is connected to contact 80(2) that is connected to line 82 and a holding circuit for said coil is provided by means of contacts 80(2) and a line 84 connected to line 82 at a location between normally open contacts 79(2) and normally closed contacts 78(2).

Switch 79 is actuated by physical contact with a pro jecting lug or member connected to the endless belt or chain feed device 58 so that such actuation of switch 79 occurs upon completion of the feeding of a tray 10 into drive 15 from the movable table 52. As noted here tofore, contacts 79(1) and 79(2) are normally open so that such actuation at the completion of the feeding cycle operates to cause these contacts to close.

Switch 78 is similar to switch 79 in that it is actuated by physical contact but differs in that its contacts 78(1) and 78(2) are normally closed and become opened when the switch is physically actuated. Switch 78 is mounted in such a location that the switch will be actuated and its contacts opened when the movable table 52 returns to its initial position and in proper alignment with the level of the waiting station 13 thus insuring that the table is in proper position to receive a subsequent tray The sequence of operations and the operation of the apparatus thus far described proceeds in the manner now to be described. Initially, an unloaded tray is in proper position at the tray loading station 12. While the tray 10 remains at the loading station, material or objects to be dried are placed thereon following which, the tray is pushed either manually or automatically to the waiting station 13. When the empty movable table 52 is properly aligned with the level of station 13, an operator places selector switch 62 in any desired one of positions 1 through 5 inclusive that corresponds with the level at which it is desired to insert the tray into the drier 15. The operation of the feeding device 50 is then initiated to push the tray from the waiting station 13 onto table 52. For purposes of illustration, it will be assumed that the operator has selected position No. 1 which corresponds with the lowermost row of rails 34 in the drier 15, thus calling for table 52 to move downwardly from the level of station 13 to a lower level corresponding with that of said lowermost of rails 34. Electrical energy is thereby supplied from contact 62(L) to contact 62(1) but electrical energy is not supplied to contacts 62(2) 62 inclusive while the selector switch remains in position- 1. Since the table 52 is in its initial position and in alignment with waiting station 13, both sets of contacts of switch 78 are open and, hence, line 77 is an open line. Thesupply of energy to contacts 62(1) energizes solenoid 76s thereby causing cylinder unit 70c to move to its extended position. The contacts of switch 60 are now closed because of the presence of a tray on table 52 so that electrical energy flows through line 67, switches 60 and" 61 and thus energizes solenoid 56 thus causing the table 52 to descend to the desired level. When the table 52 arrives at the desired level, the extended position of cylinder 70c engages switch 61 thereby opening its normally closed contacts 61D and simultaneously closing normally open contacts 611. The opening of contacts 61D interrupts line 67 thereby resulting in de-energizing of solenoid 56 and thus stopping further movement of table 52. Simultaneously, the closing of contacts 61F energizes the coil of relay 69 thereby starting operation of the feeding device 58'. Feeding continues until the tray has been pushed from the table 52 into the drier 15. Completion of the push-in operation is determined and signalled when the lug or projecting member carried by feed-in device 58 actuatesswitch 79.

As soon as table 52 moved away from the level of waiting station 13, it became disengaged from switch '78 so that its normally closed contacts are now closed. Actuation of switch 79 and the resulting closing of its normally open contacts thus completes a circuit from selector switch contacts 62(1) through switch 78 and switch 79 to energize the coil of relay 75 which is maintained in an energized condition by holding line 83. When the coil of relay 75 becomes energized, its normally open contacts 75(1) become closed thereby completing a power supply circuit for pump 55 through line 76, now closed contacts 75(1) and line 65 which is con nected to contacts 62(L). Operation of the pump unit 55 causes the table 52 to move upward from lowermost position No. 1 and such movement continues until the table again arrives at its initial position and in alignment with the level of waiting station 13 at which time the table movement is stopped automatically due to the opening of switch contacts 78(1) thereby tie-energizing relay 75 and stopping the operation of pump unit 55. The table is now in position to receive a subsequent tray 10 from waiting station 13" and for the entire cycle of operation to be repeated. With the apparatus and the controls as described, the table 52 will continue to receive trays 10, deliver them to level No. 1 and return to receive a subsequent tray, all the while continuing to deliver trays into the oven at level No. 1 until the operator selects a different level by manipulation of selector switch 62. If the operator selects positions 3, 4 or 5 which require an initially upward instead of a downward movement of table 52, operation is similar to and is controlled in a manner similar to that described above except that initially the table is caused to move upwardly by energizing relay 64 through line 63 and switch contacts 60U and 61U instead of line 67 and switch contacts 60D and 61D. And one of cylinder units 7274C is extended to sense the proper level at which the upward movement of the table 52 is arrested, and line 82 energizes relay 80 to energize the down solenoid 56 to return the table to its initial position, I

As is best illustrated in FIGURE 4, when a tray 10 is pushed into the drier at the entrance end thereof, such action results in another tray 10 being pushed out of the drier; at the discharge end thereof. The tray 10 containing the now dried material or objects is unloaded and the empty tray is returned in a chute 16 provided with a conveyor 17 which may be also of the endless or chain type of feeding device. If desired, conveyor 17 may extend throughout the entire length of chute 16 or, alternatively, the trays may be returned by gravity along chute 16' until they reach conveyor 17 which is disposed adjacent' and extending partially into the tray turn station 19. Within the area of the tray turn station 19, chute 16 is provided with a curved wall 16a which assists in the turning of a returned tray 10 substantially through an angle of 90' degrees.

As is best illustrated in FIGURE 5, the direction of movement of conveyor 17 is substantially parallel with the longitudinal axis of chute 16 at the approach to and into the tray turn station 19. Conveyor 18 moves in a direction away from waiting station 13 and substantially normal to the direction of movement of conveyor 17.

The ready station is disposed adjacent the tray turn station 19 and includes a conveyor 22 which moves in a direction opposite and parallel to that of conveyor 18.

Thus, as the operator unloads trays at the discharge end of drier 15 and returns them along chute 16, the tray is turned through an angle of approximately 90 until it assumes the position indicated by rectangle 19a within turn station 19. Cylinder 217 is then actuated which results in the turned tray being pushed to position indicated by rectangle 19a to the ready station 21. Thereafter, the tray is fed from ready station 21 by conveyor 22 to the tray loading station 12.

Turning of the trays, feeding thereof, operation of the apparatus and control of the various steps in proper se quence is achieved in a manner now to be described.

Referring to FIGURES 5 and 6, motors 85, 86, 87 are provided for driving conveyors 22, 18 and 17, respectively tarter relays 88, 89, 99 are provided for controlling the operation of motors 85, 86, 87 respectively.

Motor is started and stopped in proper sequence with other operations in the following manner. A switch 91 having a pair of normally open contacts is mounted at waiting station 13. Switch 91 is of the type that is actuated by physical contact and it is located within waiting station 13 when a loaded tray has been pushed onto that station from the tray loading station 12. A switch 92 havin a pair of normally closed contacts is mounted at ready station 21 in such a location that a member or lug carried by conveyor 22 will physically actuate switch 92 when a tray has been pushed from station 21 to the tray loading station 12. Thus, when a tray has been pushed from loading station 12 to waiting station 13, the tray 10 physically engages switch 91 and closes its normally open contacts to complete a circuit series connected with normally closed contacts of switch 92 to energize the coil of starter relay 88 and thus start motor 85. The coil is connected to one contact of the lower pair of normally open contacts of starter relay 88 and the other is series connected with switch 92 to provide a holding circuit for continuing the operation of the motor once it has been started. Upon completion of the pushing operation of a tray 10' from ready station 21 to tray loading station 12, the projecting member or lug carried by conveyor 22 engages switch 92 opening its normally closed contacts and thus interrupting the energizing circuit for starter relay 88 and stopping motor 85.

Motor 86 is controlled in a similar manner by starter relay 89 and the upper pair of normally open contacts of switch 93 and the normally closed contacts of a switch 94. Switch 9 4 is mounted adjacent conveyor 18 so that a member or lug projecting therefrom will actuate switch 94 to stop the motion of the conveyor upon completion of the turning operation.

Switch 93 performs a dual function of starting motor 86 and simultaneously stopping the operation of motor 87. Switch 93 is also of the type wherein physical engagement with the switch actuates the contacts thereof and it is located in a position where it is engaged by a tray 10 as such tray is fed by conveyor 17 from chute 16 into proper position just prior to the commencement of the turning operation. At such time, actuation of switch 93 by a tray ready for a turning operation, results in the simultaneous closing of the upper normally open pair of contacts and the opening of the normally closed pair of contacts of switch 93. Said normally closed contacts are series connected with the source of electrical energy and the holding circuit for starter relay 90.

Switch 95 is also of the type that is actuated by physical engagement. It is located adjacent conveyor 22 and also adjacent tray loading station 12 so that it is engaged by a projecting member or lug carried by conveyor 22 when a tray has been pushed from ready station 21 onto tray loading station 12 and ready station 21 is thus free to receive a subsequent tray. Switch 95 has two pairs of normally open contacts parallel connected with each other and series connected with the normally closed contacts of switch 93.

The upper pair of contacts of switch 95 is connected to the coil of starter relay 90 and the lower pair is connected to the coil 20A of cylinder 20. The right hand contact of the lower set of normally open contacts of starter relay 90 is series connected with the normally closed contacts of switch 93 and thus provides a holding circuit for maintaining the coil of starter relay 90 in an energized condition once it has been initially energized.

Thus, the return of unloaded trays from the discharge end of drier 15 including the various pushing and turning operations and ultimately delivering such unloaded tray to tray loading station 12 is accomplished in the following manner. When a loaded tray 10 is pushed from tray loading station 12 to waiting station 13, the tray 10 engages switch 91 and closes its normally open contacts, thus starting motor 85 and the urging by conveyor 22 of an unloaded tray from ready station 21 toward tray loading station 12. When the tray has been pushed clear from ready station 21, switch 95 is engaged thereby simultaneously closing both sets of its normally open contacts and simultaneously starting the operation of motor 87 to drive conveyor 17 and also to energize coil 20A of cylinder 20. When solenoid 20A is energized, this causes cylinder 20 to move to its extended position carrying with it a turned tray 10 from tray station 19 to ready station 21. Conveyor 17 moves a next adjacent tray along chute 16 until the tray comes into proper position prior to turning at which time it engages switch 93. Such engagement simultaneously closes the normally open con tacts of switch 93 thereby initiating operation of motor 86 and conveyor 18 and the opening of its normally closed contacts stops the operation of motor 87 and conveyor 17. The operation of conveyor 18 turns the tray into position for subsequent delivery to the tray ready station 21 by the action of cylinder 20.

While particular embodiments of the invention have been illustrated and described, it will be apparent that various changes and modifications may be made without departing from the invention and it is intended in the appended claims to cover all such changes and modifica tions that fall within the true spirit and scope of the invention.

What is claimed is:

1. A method of drying including the steps of moving material to be dried between oppositely disposed walls of a drying chamber from an entrance thereto along a selected one of a plurality of paths disposed at differing levels within said chamber, introducing heated fluent material into said chamber through said walls in a plurality of individual streams extending across all of said levels and with said streams introduced through one of said Walls being displaced along the extent of said paths relative to corresponding streams introduced through the other of said walls, directing said streams angularly relative to said walls and toward a corresponding displaced stream introduced through the opposite wall to cause flow of the fluent material in a direction generally opposite to the direction of movement of the material to be dried and along a sinuous path between said walls and extending across all of said levels, and removing said fluent material from said chamber at a location adjacent said entrance.

2. A drier comprising walls defining a drying chamber having entrance and discharge ends,

means including tracks supported by said walls at differing levels extending through said chamber for conveying material to be dried through said chamber from the entrance toward the discharge end at any selected one of said levels, means for supplying and causing heated fluent material to flow along a sinuous path between said walls through all of said levels and in the general direction from said discharge toward said entrance ends, said means including spaced apart ports each extending through all of said levels disposed in opposite side walls of said chamber, the ports in one side wall being displaced along said track relative to corresponding ports in the opposite side wall with said ports being angularly disposed relative to said side walls and directed toward said entrance end and directed toward a corresponding port in the opposite side wall, and

means including an opening in said walls adjacent said entrance end for removal of said fluent material.

References Cited UNITED STATES PATENTS 1,685,026 9/1928 Hults 34-217 1,881,063 10/1932 Randolph 34-204 X 2,040,884 5/1936 Somes 34-228 X 2,612,706 10/1952 Simpson et al 34l05 3,038,585 6/1962 Beckley 34205 X KENNETH W. SPRAGUE, Primary Examiner. 

1. A METHOD OF DRYING INCLUDING THE STEPS OF MOVING MATERIAL TO BE DRIED BETWEEN OPPOSITELY DISPOSED WALLS OF A DRYING CHAMBER FROM AN ENTRANCE THERETO ALONG A SELECTED ONE OF A PLURALITY OF PATHS DISPOSED AT DIFFERING LEVELS WITHIN SAID CHAMBER, INTRODUCING HEATED FLUENT MATERIAL INTO SAID CHAMBER THROUGH SAID WALLS IN A PLURALITY OF INDIVIDUAL STREAMS EXTENDING ACROSS ALL OF SAID LEVELS AND WITH SAID STREAMS INTRODUCED THROUGH ONE OF SAID WALLS BEING DISPLACED ALONG THE EXTENT OF SAID PATHS RELATIVE TO CORRESPONDING STREAMS INTRODUCED THROUGH THE OTHER OF SAID WALLS, DIRECTING SAID STREAMS ANGULARLY RELATIVE TO SAID WALLS AND TOWARD A CORRESPONDING DISPLACED STREAM INTRODUCED THROUGH THE OPPOSITE WALL TO CAUSE FLOW OF THE FLUENT MATERIAL IN A DIRECTON GENERALLY OPPOSITE TO THE DIRECTION OF MOVEMENT OF THE MATERIAL TO BE DRIED AND ALONG A SINUOUS PATH BETWEEN SAID WALLS AND EXTENDING ACROSS ALL OF SAID LEVELS, AND REMOVING SAID FLUENT MATERIAL FROM SAID CHAMBER AT A LOCATION ADJACENT SAID ENTRANCE. 